The invention relates to methods of producing saturated polymers and blends of saturated and unsaturated polymers using transition metal catalysts, particularly involving ring-opening metathesis polymerisation (ROMP).
Metathesis polymerisation techniques, though increasingly broad in scope, generate unsaturated polymers which are limited in their applications by the susceptibility of the olefinic linkages to oxidative and thermal degradation (1,2,3). Facile routes to the saturated polymers are thus attractive. Ring-opening metathesis polymerisation (ROMP), followed by hydrogenation, offers a xe2x80x9cback-doorxe2x80x9d route to high-molecular weight, narrow-polydispersity polyolefins, with structures or functionalities inaccessible via conventional Ziegler-Natta or metallocene catalysis. Current methods for reduction of ROMP polymers focus largely on stoichiometric techniques, of which diimide reduction is most common, despite the expense of the p-toluenesulfonhydrazide precursor on a large scale, and evidence for contamination of the polymer by p-toluenesulfonyl groups (4). Limited success has been reported in catalytic reduction via palladium and nickel species (1) though quantitative hydrogenation has been described using RuHCl(CO)(PCy3)2 (xe2x80x9cCyxe2x80x9d=cyclohexyl) at elevated temperatures and pressures (165xc2x0 C., 1400 psi) (2). This Ru species was also the most active catalyst found for reduction of structurally related polybutadiene rubbers by an extensive series of ruthenium catalysts (5). With internal olefins, similarly forcing conditions were invariably required. A one-pot polymerisation of 1,5-cyclooctadiene to yield a saturated product, using a bimetallic Ru catalyst has previously been reported (6).
U.S. Pat. No. 5,312,940 issued May 17, 1994, and U.S. Pat. No. 5,342,909 issued Sep. 10, 1996 (both in the name of Grubbs et al.) disclose compounds and the process for their production, which include compounds of the formula I below (these compounds will hereinafter be termed ""Grubb""s catalyst): 
wherein;
R is selected from hydrogen, or a broad range of organic groups;
each X is independently selected from any anionic ligand;
each L is independently selected from any neutral electron donor; and
wherein any 2, or 3 of each X, and each L, are optionally bonded together to form a chelating agent multidentate ligand.
Compounds encompassed by Grubbs""s catalyst are known in the art to be suitable as catalysts for metathesis polymerisation of cyclic olefins. For example, U.S. Pat. No. 5,932,664 issued Aug. 3, 1999, discloses a process for the production of hydrogenated, ring-opened metathesis (co) polymers from cyclic olefins via catalysis using a similar range of compounds in an inert solvent, wherein the catalyst is optionally modified after polymerisation by adding a modifier, followed by hydrogenation without the addition of extra catalyst. U.S. Pat. No. 5,932,664 claims a system wherein the hydrogenation step can occur at pressures between 2 and 200 bar. Typical ROMP polymerisation and subsequent hydrogenation reactions, which utilize the same catalyst, are known in the art as xe2x80x98tandemxe2x80x99 ROMP-hydrogenation reactions, in which a single catalyst effects both polymerisation and hydrogenation/hydrogenolysis steps.
In this regard, the inventors (6) and others (8-12) have focused on development of tandem ROMP-hydrogenation, in which both processes are effected by a single catalyst precursor (as shown in equation 1 below): 
wherein R is selected from hydrogen or a broad range of organic groups, and n is variable depending upon stoichiometry, and is general in the range of 1-1000.
It is an object of the invention to improve the efficiency of ROMP-hydrogenation or ROMP-hydrogenolysis processes, and the utility of the materials obtained therefrom. Thus the invention provides a means for increasing the rate of reaction of the hydrogenation step of the ROMP-hydrogenation process as well as a means to perform multiple ROMP-hydrogenation or hydrogenolysis reaction cycles in a xe2x80x98one-potxe2x80x99 reaction. Moreover, the present invention discloses ROMP-hydrogenation reactions that may be carried out at pressures as low as atmospheric pressure.
In a first embodiment, the present invention provides for a method for producing a substantially saturated polymer, the method comprising the steps of:
(A) generating an unsaturated polymer by polymerising a substrate using ring-opening metathesis polymerisation (ROMP) in the presence of a catalyst comprising a carbene group, the catalyst being of the formula I: 
xe2x80x83wherein each L represents independently a neutral two electron donor ligand, each X represents independently a co-ordinating anion, and any two or more of X and L may be connected via a bridging moiety, and R represents hydrogen or an organic radical, to form an unsaturated polymer;
(B) hydrogenating the unsaturated polymer to produce the substantially saturated polymer, wherein the hydrogenation is catalysed by a hydrogenation catalyst generated by modification of the polymerisation catalyst of formula I by replacement of the carbene group with at least one hydrogen, and the hydrogenation reaction is accelerated by a catalysis enhancing non-inert solvent; and
(C) adding a Lewis or Brxc3x6nsted acid or base at any time prior to step (B), as required.
In a second embodiment, the invention provides for a method for producing a polymer, the method comprising the steps of:
(A) generating an unsaturated polymer by polymerising a substrate using ring-opening metathesis polymerisation (ROMP) in the presence of a catalyst comprising a carbene group, the catalyst being of the formula I: 
xe2x80x83wherein each L represents independently a neutral two electron donor ligand, each X represents independently a coordinating anion, and any two or more of X and L may be connected via a bridging moiety, and R represents hydrogen or an organic radical, to form an unsaturated polymer;
(B) hydrogenation of the unsaturated polymer to produce the substantially saturated polymer, wherein the hydrogenation is catalysed by a hydrogenation catalyst generated by modification of the polymerisation catalyst of formula I by replacement of the carbene group with at least one hydrogen; and
(C) adding a Lewis or Brxc3x6nsted acid or base at any time prior to step (B), as required;
(D) regenerating the polymerisation catalyst of formula I by reinstallation of the carbene group; and
(E) adding a substrate, which may differ from the substrate of step (A), as required;
(F) performing a second polymerisation step, catalysed by the polymerisation catalyst of formula I, as regenerated in step (D).
In a third embodiment, there is provided a method for producing a substantially saturated polymer, the method comprising the steps of:
(A) generating an unsaturated polymer by polymerising a substrate using ring-opening metathesis polymerisation (ROMP) in the presence of a catalyst comprising a carbene group, the catalyst being of the formula I: 
xe2x80x83wherein each L represents independently a neutral two electron donor ligand, each X represents independently a co-ordinating anion, and any two or more of X and L may be connected via a bridging moiety, and R represents hydrogen or an organic radical, to form an unsaturated polymer;
(B) hydrogenating the unsaturated polymer to produce the substantially saturated polymer, wherein the hydrogenation is catalysed by a hydrogenation catalyst generated by modification of the polymerisation catalyst of formula I by replacement of the carbene group with at least one hydrogen, under a hydrogen pressure of from about 1 to about 200 bar; and
(C) adding a Lewis or Brxc3x6nsted acid or base at any time prior to step (B), as required.
In a fourth embodiment, there is provided a method for producing a substantially saturated polymer, the method comprising the steps of:
(A) generating an unsaturated polymer by polymerising a substrate using ring-opening metathesis polymerisation (ROMP) in the presence of a suitable catalyst;
(B) hydrogenating the unsaturated polymer to produce the substantially saturated polymer, wherein the hydrogenation is catalysed by a hydrogenation catalyst generated by modification of the polymerisation catalyst of formula I by replacement of the carbene group with at least one hydrogen, and the hydrogenation reaction is accelerated by a catalysis enhancing non-inert solvent; and
(C) adding a Lewis or Brxc3x6nsted acid or base at any time prior to step (B), as required.
In a fifth embodiment, there is provided a method for producing an unsaturated polymer, the method comprising the steps of:
(A) generating an unsaturated polymer by polymerising a substrate using ring-opening metathesis polymerisation (ROMP) in the presence of a catalyst comprising a carbene group, the catalyst being of the formula I: 
xe2x80x83wherein each L represents independently a neutral two electron donor ligand, each X represents independently a co-ordinating anion, and any two or more of X and L may be connected via a bridging moiety, and R represents hydrogen or an organic radical, to form an unsaturated polymer;
(B) subjecting the unsaturated polymer to hydrogenolysis, wherein the hydrogenolysis is effected by a hydrogenolysis agent generated by modification of the polymerisation catalyst of formula I by replacement of the carbene group with at least one hydrogen, under a hydrogen pressure of less than about 1 atm; and
(C) adding a Lewis or Brxc3x6nsted acid or base at any time prior to step (B), as required.